Carbon dioxide storage tank for supercritical extraction

Abstract

This invention discloses a carbon dioxide storage tank for supercritical extraction, belonging to the field of supercritical extraction technology. It includes a tank body, an inlet, and an outlet. The inlet connects to a carbon dioxide supply source, and the outlet connects to the delivery pipeline of the supercritical extraction vessel. It also includes a buffer mechanism to absorb pressure fluctuations generated during filling and output. The buffer mechanism includes an inner cylinder, a first piston, a connecting hole, and an elastic support. By setting an inner cylinder, a first piston dividing the inner cylinder's cavity into an upper and lower cavity, and a connecting hole at the bottom of the inner cylinder, this invention can quickly absorb pressure spikes generated during filling and output, and actively increase pressure during output to prevent sudden pressure drops. Compared to existing fixed inner cylinders or unbuffered storage tanks, this invention achieves dual-degree-of-freedom buffering through the movement of the first piston and the overall movement of the inner cylinder, significantly improving the efficiency of pressure fluctuation absorption.

Description

Technical Field

[0001] This invention belongs to the field of supercritical extraction technology, specifically relating to a carbon dioxide storage tank for supercritical extraction. Background Technology

[0002] Supercritical carbon dioxide extraction technology utilizes the properties of carbon dioxide in a supercritical state (temperature ≥31.1℃, pressure ≥7.38MPa), which combines gas diffusion and liquid solubility, to extract and separate target components. It has advantages such as being non-toxic, residue-free, pollution-free, and having a low extraction temperature, and is widely used in natural product extraction, pharmaceuticals, chemicals, and food processing. In a supercritical extraction system, the carbon dioxide storage tank is one of the core pieces of equipment, and its function is to stably provide liquid or supercritical carbon dioxide to the extraction vessel.

[0003] However, existing carbon dioxide storage tanks for supercritical extraction have certain technical problems in practical use. During the filling and output of liquid carbon dioxide, pressure fluctuations are prone to occur inside the tank. The high pressure impact during filling can easily form instantaneous pressure peaks, and the pressure drop during output can easily occur due to changes in flow rate or intermittent gas use. This not only affects the stability of the feed, but may also cause cavitation of the delivery pump, or even cause premature vaporization of liquid carbon dioxide, affecting the normal operation of the extraction system. At the same time, most of the current storage tanks adopt a single cavity structure and lack an effective built-in buffer mechanism, which makes it difficult to quickly absorb and smooth pressure fluctuations, resulting in insufficient pressure control accuracy of the extraction system and long-term operational reliability that needs to be improved. To avoid the aforementioned technical problems, it is indeed necessary to provide a carbon dioxide storage tank for supercritical extraction to overcome the deficiencies in the prior art. Summary of the Invention

[0004] The purpose of this invention is to provide a carbon dioxide storage tank for supercritical extraction to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a carbon dioxide storage tank for supercritical extraction, comprising a tank body, an inlet and an outlet, wherein the inlet is used to connect to a carbon dioxide supply source, and the outlet is used to connect to a delivery pipeline of a supercritical extraction vessel, characterized in that it further comprises a buffer mechanism for absorbing pressure fluctuations generated during filling and output. The buffer mechanism includes: An inner cylinder is disposed inside the tank body, which divides the interior of the tank into an outer cavity and an inner cavity. The outer cavity is connected to the liquid inlet and the liquid outlet as the main storage cavity. The first piston is disposed inside the inner cylinder. The inner cavity is divided into an upper cavity and a lower cavity. The upper cavity is a sealed cavity containing high-pressure gas. A connecting hole is provided at the bottom of the inner cylinder, through which the lower cavity communicates with the outer cavity; An elastic support is provided between the bottom of the inner cylinder and the bottom of the tank to float and support the inner cylinder.

[0006] As a preferred embodiment, the upper cavity is provided with a guide reset mechanism, including a sleeve rod fixed to the top of the upper cavity, a telescopic rod fixedly connected to the first piston, and a telescopic spring sleeved on the outer wall of the sleeve rod and the telescopic rod. The telescopic rod passes through the sleeve rod and is axially slidably connected to it.

[0007] As a preferred embodiment, the inner wall of the inner cylinder is provided with reinforcing ribs, which are annular ribs, longitudinal ribs or a combination thereof, and are distributed gradually from bottom to top along the axial direction of the inner cylinder.

[0008] As a preferred embodiment, it further includes an auxiliary mechanism, which includes: A balance tank, the balance tank penetrating the upper cavity of the inner cylinder, the balance tank being isolated from the upper cavity; The second piston is disposed inside the balance tank, which is divided into a second balance chamber and a connecting chamber. The second balance chamber is a sealed cavity containing high-pressure gas.

[0009] A balance hole is provided on the balance tank to connect the connecting cavity with the gas phase space of the outer cavity.

[0010] As a preferred embodiment, multiple balance tanks are provided, and the multiple balance tanks are evenly arranged along the circumference of the inner cylinder.

[0011] In a preferred embodiment, a connecting ring is fixedly provided on the inner wall of the tank, and a sealing plate is fixed on the inner wall of the connecting ring. The sealing plate and the balance hole are arranged opposite each other in the axial direction so that the overlap area between the balance hole and the sealing plate changes when the inner cylinder moves in the axial direction.

[0012] In a preferred embodiment, the elastic support includes a connecting piece and a guide rod, the guide rod passing through the connecting piece and slidably connected thereto, for limiting the circumferential rotation and radial displacement of the inner cylinder.

[0013] In a preferred embodiment, the elastic support further includes a sleeve and a shape memory alloy spring, the shape memory alloy spring being sleeved on the guide rod, the stiffness of which increases with increasing temperature and decreases with decreasing temperature.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention, by setting an inner cylinder, a first piston that divides the inner cylinder cavity into an upper cavity and a lower cavity, and a connecting hole at the bottom of the inner cylinder, can quickly absorb pressure spikes generated during filling and output, and actively increase pressure during output to prevent sudden pressure drops. Compared with existing fixed inner cylinders or unbuffered storage tanks, it achieves dual-degree-of-freedom buffering of the movement of the first piston and the overall movement of the inner cylinder, which greatly improves the pressure fluctuation absorption efficiency.

[0015] This invention, by setting up a balance tank, a second piston, and a second balance chamber isolated from the upper cavity, allows the inner cylinder to automatically sink when the pressure rises due to liquid absorption and weight gain, thereby increasing the overlap area between the balance hole and the sealing plate and reducing the gas flow area, thus suppressing a sudden pressure rise. When the pressure decreases, the inner cylinder floats up, opening the balance hole, and high-pressure gas in the second balance chamber replenishes the outer cavity, preventing negative pressure flash evaporation. At the same time, it forms a pressure hysteresis differential, preventing frequent system oscillations. The second piston and the second balance chamber provide a secondary buffer when the balance hole is blocked, protecting the throttling structure. Compared with existing technologies that rely on external valves or fixed throttling holes, this technology achieves decoupling of gas throttling and liquid buffering, relies entirely on gravity drive, requires no external energy, and the multi-tank layout ensures balanced force distribution and redundancy reliability in the inner cylinder. This invention employs a shape memory alloy spring as part of the elastic support, fitted onto a guide rod to form a temperature self-compensation mechanism. The spring's stiffness increases with increasing temperature and decreases with decreasing temperature near the supercritical extraction set temperature, requiring different weights for the inner cylinder to sink at different temperatures. This automatically adjusts the system's equilibrium pressure to follow changes in carbon dioxide saturated vapor pressure, achieving fully mechanical temperature compensation. When the temperature rises abnormally, the stiffness increases, making it less likely for the inner cylinder to sink and avoiding low-pressure safety risks. When the temperature drops abnormally, the stiffness decreases, making it easier for the inner cylinder to sink and preventing vaporization caused by excessively low pressure. Temperature and pressure coupling control is achieved through the phase change characteristics of the shape memory alloy spring itself, resulting in a simpler structure, more direct response, and suitability for long-term stable operation under high-pressure environments. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the three-dimensional structure of the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the three-dimensional structure of the present invention. Figure 2 ; Figure 3 This is a schematic diagram of the internal structure of the tank of the present invention. Figure 1 ; Figure 4 This is a schematic diagram of the internal structure of the tank of the present invention. Figure 2 ; Figure 5 This is a schematic diagram of the auxiliary mechanism structure of the present invention; Figure 6This is a schematic diagram of the connecting ring structure of the present invention; Figure 7 This is a schematic diagram of the inner cylinder structure of the present invention; Figure 8 This is a schematic diagram of the internal structure of the inner cylinder of the present invention.

[0017] In the diagram: 1. Tank body; 2. Inlet; 3. Outlet; 4. Inner cylinder; 5. Outer cavity; 6. Inner cavity; 7. Upper cavity; 8. Lower cavity; 9. Connecting hole; 10. Elastic support; 11. Balance tank; 12. Second piston; 13. Second balance cavity; 14. Connecting cavity; 15. Connecting ring; 16. Sealing plate; 17. Connecting piece; 18. Guide rod; 19. Sleeve; 20. Sleeve rod; 21. Telescopic rod; 22. Telescopic spring; 23. First piston. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments.

[0019] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0020] Please see Figures 1-8 The present invention provides a carbon dioxide storage tank for supercritical extraction, including a tank body 1, an inlet 2 and an outlet 3. The inlet 2 is used to connect to a carbon dioxide supply source, and the outlet 3 is used to connect to the delivery pipeline of the supercritical extraction vessel. It also includes a buffer mechanism to absorb pressure fluctuations that occur during filling and discharging; By incorporating a buffer mechanism, pressure fluctuations during filling and output are converted into mechanical energy for absorption, thus preventing pressure shocks from being directly transmitted to the extraction vessel and ensuring a stable extraction process. Compared to existing technologies that lack buffering or rely solely on pipeline damping, this approach actively absorbs pressure spikes, significantly reducing the risk of pump cavitation. The buffer mechanism includes: The inner cylinder 4 is located inside the tank 1. The inner cylinder 4 divides the inside of the tank 1 into an outer cavity 5 and an inner cavity 6. The outer cavity 5 is connected to the liquid inlet 2 and the liquid outlet 3 and is the main storage cavity. The first piston 23 is located inside the inner cylinder 4. The inner cavity 6 is divided into an upper cavity 7 and a lower cavity 8. The upper cavity 7 is a sealed cavity containing high-pressure gas. A connecting hole 9 is provided at the bottom of the inner cylinder 4, and the lower cavity 8 is connected to the outer cavity 5 through the connecting hole 9; The elastic support 10 is disposed between the bottom of the inner cylinder 4 and the bottom of the tank 1 to float and support the inner cylinder 4. The inner cylinder 4 and the first piston 23 cooperate with each other. By utilizing the compressibility of the sealed gas in the upper cavity 7, the liquid pressure fluctuation is converted into gas compression energy, achieving rapid buffering. At the same time, the elastic support 10 allows the inner cylinder 4 to float as a whole, providing a basis for subsequent gravity-driven throttling. Compared with the existing fixed inner cylinder structure, it achieves dual-degree-of-freedom buffering of piston movement and overall movement of the inner cylinder 4, significantly improving the absorption efficiency of pressure fluctuations. When the pressure in the outer cavity 5 decreases, the high-pressure gas in the upper cavity 7 expands, pushing the first piston 23 downwards. This forces the liquid in the lower cavity 8 back into the outer cavity 5 through the connecting hole 9, thus achieving active pressurization of the outer cavity 5. This mechanism effectively prevents a sudden drop in pressure during the output process, avoiding premature vaporization of liquid carbon dioxide due to excessively low pressure, and ensuring that the carbon dioxide delivered to the extraction vessel remains in a stable liquid or supercritical state.

[0021] A guide reset mechanism is provided inside the upper cavity 7. The guide reset mechanism includes a sleeve rod 20, a telescopic rod 21 and a telescopic spring 22. The sleeve rod 20 is fixed to the top of the upper cavity 7, the telescopic rod 21 is fixedly connected to the first piston 23, and the telescopic rod 21 passes through the sleeve rod 20 and is axially slidably connected to it. The telescopic spring 22 is sleeved on the outer wall of the sleeve rod 20 and the telescopic rod 21. The guide reset mechanism ensures that the first piston 23 moves linearly within the upper cavity 7, preventing piston wear. Simultaneously, the telescopic spring 22 assists in piston reset when pressure decreases, improving response consistency. Compared to a piston structure without a guide, this guide reset mechanism effectively extends the sealing life and ensures stable piston return under different pressures. Furthermore, the telescopic spring 22 generates elastic damping during piston movement, absorbing the energy of pressure fluctuations a second time and further reducing impact. This damping effect, combined with the buffering effect of the gas in the upper cavity 7, enhances the energy absorption capacity of the entire buffer mechanism.

[0022] The inner wall of the inner cylinder 4 is provided with reinforcing ribs, which are annular ribs, longitudinal ribs or a combination thereof, and are gradually distributed from the bottom to the top along the axial direction of the inner cylinder 4. By setting reinforcing ribs, the total weight of the inner cylinder 4 is reduced while ensuring the compressive strength of the inner cylinder 4, thereby improving the sensitivity of the inner cylinder 4 to gravity sinking. Compared with the inner cylinder 4 of equal wall thickness, this reinforcing rib structure is lighter in weight under the same strength, which makes the floating response speed of the inner cylinder 4 faster. At the same time, the reinforcing rib significantly improves the radial rigidity and resistance to elliptical deformation of the inner cylinder 4. Under high pressure differential conditions, the inner cylinder 4 bears a huge pressure difference between the high pressure of the outer cavity 5 and the low pressure of the inner cavity 6. The reinforcing rib can effectively maintain the roundness of the inner cylinder 4 and prevent uneven sealing gap between the first piston 23 and the inner wall of the inner cylinder 4 due to deformation, thereby ensuring the sealing reliability and smooth piston movement during long-term operation.

[0023] It also includes an auxiliary mechanism, which includes a balance tank 11 that penetrates the upper cavity 7 and is isolated from the upper cavity 7. The second piston 12 is located inside the balance tank 11, dividing the inside of the balance tank 11 into a second balance chamber 13 and a connecting chamber 14. The second balance chamber 13 is a sealed chamber containing high-pressure gas. The balance tank 11 has a balance hole that connects the connecting cavity 14 to the gas phase space of the outer cavity 5. Multiple balance tanks 11 are provided, and the multiple balance tanks 11 are evenly arranged along the four circumferences of the inner cylinder. By setting up a balance tank 11 and a second piston 12 to form a gas throttling and secondary buffer, when the inner cylinder 4 sinks, the balance hole is partially blocked by the sealing plate 16, the gas exchange is blocked, thereby suppressing the pressure rise. When the inner cylinder 4 floats up, the balance hole is fully opened and the auxiliary pressure is restored. Multiple balance tanks 11 are evenly arranged in the circumference, which can make the inner cylinder 4 bear the force evenly and avoid tilting. Compared with the single channel structure, the decoupling of gas throttling and liquid buffering is realized, and the multi-tank layout improves the redundancy and reliability of the system. A connecting ring 15 is fixedly installed on the inner wall of the tank body 1, and a sealing plate 16 is fixedly installed on the inner wall of the connecting ring 15. The sealing plate 16 and the balance hole are arranged opposite each other in the axial direction so that when the inner cylinder 4 moves in the axial direction, the overlapping area of ​​the balance hole and the sealing plate 16 changes accordingly. The sealing plate 16, as a fixing component, forms a variable throttling mechanism with the balance hole. When the inner cylinder 4 sinks, the overlapping area between the balance hole and the sealing plate 16 increases, and the gas flow area decreases. When the inner cylinder 4 floats, the overlapping area decreases, and the gas flow area increases, which can form a pressure hysteresis differential and prevent the system from oscillating frequently near the equilibrium point. When the pressure in the outer cavity 5 decreases, the inner cylinder 4 floats up, reducing the overlap area between the balance hole and the sealing plate 16 or even completely separating them. This increases the gas flow area, and the gas exchange between the gas phase space of the outer cavity 5 and the connecting cavity 14 is restored. At this time, the high-pressure gas in the connecting cavity 14 or even the second balance cavity 13 can be replenished to the outer cavity 5 through the balance hole, thereby preventing the outer cavity 5 from generating excessive negative pressure. This avoids the flash evaporation of liquid carbon dioxide caused by negative pressure, ensuring the purity of the output medium and the suction performance of the pump. The elastic support 10 includes a connecting piece 17 and a guide rod 18. The guide rod 18 passes through the connecting piece 17 and is vertically slidably connected to it to limit its circumferential rotation and radial offset. The elastic support also includes a sleeve 19 and a shape memory alloy spring. The shape memory alloy spring is located inside the sleeve 19 and is sleeved on the guide rod 18 located inside the sleeve 19. Its stiffness increases with increasing temperature and decreases with decreasing temperature. The guide rod 18 and the connecting piece 17 constitute an anti-rotation and anti-deviation mechanism, ensuring that the inner cylinder 4 moves only along the axial direction to avoid jamming. The balance tank 11 and the sealing plate 16 are fixed in relative positions in the circumferential and radial directions, so that the axial overlap between the balance hole and the sealing plate 16 depends only on the axial displacement of the inner cylinder 4 and is unrelated to the rotation or deflection of the inner cylinder 4, thus ensuring the repeatability and stability of the gas throttling characteristics and avoiding changes in throttling performance due to assembly deviations or operational drift. The shape memory alloy spring allows the stiffness of the elastic support 10 to automatically adjust with temperature: The stiffness automatically adjusts with temperature, and also provides additional safety protection. When the temperature rises abnormally, the increased stiffness of the shape memory alloy spring makes the inner cylinder 4 less likely to sink, thereby avoiding the safety risks caused by the system maintaining low pressure at excessively high temperatures. Conversely, when the temperature drops abnormally, the decrease in spring stiffness makes the inner cylinder 4 sink more easily, which can avoid the risk of vaporization caused by excessively low pressure, and at the same time has the dual functions of pressure self-adaptation and extreme condition protection.

[0024] When the temperature rises, the stiffness increases, and the inner cylinder 4 requires more weight to sink, causing the balance pressure to rise automatically. When the temperature drops, the stiffness decreases, and the balance pressure drops automatically. Compared with existing technology that uses ordinary springs, this design achieves fully mechanical temperature compensation.

[0025] Working principle and usage process of this invention: Liquid carbon dioxide enters the main storage chamber through the inlet 2. A portion of the liquid enters the lower chamber 8 through the connecting hole 9 at the bottom of the inner cylinder 4, pushing the first piston 23 to move upward and compressing the high-pressure gas sealed in the upper chamber 7. This converts the filling pressure peak into gas compression energy, achieving rapid buffering.

[0026] Simultaneously, the liquid entering the inner cylinder 4 increases its total weight. Under the influence of gravity, the inner cylinder 4 moves downward as a whole, compressing the elastic support 10 at the bottom. The sinking of the inner cylinder 4 causes the balance tank 11 to move downward synchronously, allowing the balance hole to gradually enter the area of ​​the sealing plate 16. The overlap area between the balance hole and the sealing plate 16 increases, the gas flow area decreases, and the gas exchange in the gas phase space of the outer cavity 5 is obstructed, thereby inhibiting further pressure increases.

[0027] During this process, the pressure change in the connecting cavity 14 drives the second piston 12 to move, compressing the gas in the second balance cavity 13 to form a secondary buffer, protecting the balance hole and the sealing plate 16 from pressure shock.

[0028] When filling is complete and the system pressure is stable, the inner cylinder 4 is in a certain intermediate equilibrium position, the high pressure gas in the upper cavity 7 is in balance with the liquid pressure in the lower cavity 8, and the first piston 23 is stationary. The balance hole and the sealing plate 16 maintain an appropriate overlap area, ensuring normal gas exchange and maintaining the pressure inside the tank within the set range. If changes in ambient temperature cause pressure drift, the stiffness of the shape memory alloy spring automatically adjusts, changing the balance position of the inner cylinder 4, so that the system pressure follows the changes in the saturated vapor pressure of carbon dioxide.

[0029] When the outlet 3 opens to deliver carbon dioxide to the supercritical extraction vessel, the pressure in the outer cavity 5 gradually decreases. At this time, the high-pressure gas in the upper cavity 7 expands, pushing the first piston 23 downward, and actively pushing the liquid in the lower cavity 8 back into the outer cavity 5 through the connecting hole 9, thereby achieving active pressurization of the outer cavity 5 and preventing a sudden drop in output pressure and premature vaporization of liquid carbon dioxide.

[0030] Simultaneously, the total weight of the inner cylinder 4 decreases, and the elastic support 10 pushes the inner cylinder 4 upward to reset. The upward movement of the inner cylinder 4 reduces or even completely separates the overlap area between the balance hole and the sealing plate 16, increases the gas flow area, and restores unobstructed gas exchange between the gas phase space of the outer cavity 5 and the connecting cavity 14. At this time, the high-pressure gas in the connecting cavity 14 and even the second balance cavity 13 can be replenished to the outer cavity 5 through the balance hole, preventing excessive negative pressure in the outer cavity 5, avoiding flash vaporization caused by negative pressure, ensuring the purity of the output medium, and the extension spring 22 generates elastic damping during the piston reset process, further absorbing the remaining energy and making the pressure transition smoothly.

[0031] When the temperature inside the tank rises, the stiffness of the shape memory alloy spring increases, requiring the inner cylinder 4 to sink the same distance. This causes the system's equilibrium pressure to automatically increase, following the rise in the saturated vapor pressure of carbon dioxide, thus preventing premature vaporization. When the temperature decreases, the spring stiffness decreases, and the equilibrium pressure automatically decreases, preventing over-compression. This temperature compensation is achieved entirely mechanically, without the need for electrical sensors.

[0032] When the temperature rises abnormally, the increased spring stiffness makes the inner cylinder 4 less prone to sinking, avoiding the safety risks caused by maintaining low pressure at excessively high temperatures. When the temperature drops abnormally, the decreased spring stiffness makes the inner cylinder 4 easier to sink, preventing vaporization caused by excessively low pressure. At the same time, the reinforcing ribs ensure the roundness of the inner cylinder 4 under high pressure differential, preventing seal failure. The anti-rotation and anti-deviation mechanism composed of the guide rod 18 and the connecting piece 17 ensures that the inner cylinder 4 moves only axially, ensuring precise alignment between the balance hole and the sealing plate 16, making the throttling characteristics stable and reliable.

[0033] In summary, this invention achieves pure mechanical adaptive pressure stability control under all operating conditions of filling, output, and temperature changes through three complementary levels: gas buffering of the first piston 23 and the upper cavity 7, gravity sinking of the inner cylinder 4 and throttling of the balance hole, and temperature compensation of the shape memory alloy spring. It requires no external energy.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A carbon dioxide storage tank for supercritical extraction, comprising a tank body (1), an inlet (2), and an outlet (3), wherein the inlet (2) is used to connect to a carbon dioxide supply source, and the outlet (3) is used to connect to a delivery pipeline of a supercritical extraction vessel, characterized in that, It also includes a buffer mechanism to absorb pressure fluctuations that occur during filling and discharging; The buffer mechanism includes: The inner cylinder (4) is disposed inside the tank (1). The inner cylinder (4) divides the inside of the tank (1) into an outer cavity (5) and an inner cavity (6). The outer cavity (5) is connected to the inlet (2) and the outlet (3) as the main storage cavity. The first piston (23) is located inside the inner cylinder (4). The inner cavity (6) is divided into an upper cavity (7) and a lower cavity (8). The upper cavity (7) is a sealed cavity containing high-pressure gas. A connecting hole (9) is provided at the bottom of the inner cylinder (4), and the lower cavity (8) is connected to the outer cavity (5) through the connecting hole (9); An elastic support (10) is provided between the bottom of the inner cylinder (4) and the bottom of the tank (1) to float and support the inner cylinder (4).

2. The carbon dioxide storage tank for supercritical extraction according to claim 1, characterized in that: The upper cavity (7) is provided with a guide reset mechanism, including a sleeve rod (20) fixed to the top of the upper cavity (7), a telescopic rod (21) fixedly connected to the first piston (23), and a telescopic spring (22) sleeved on the outer wall of the sleeve rod (20) and the telescopic rod (21). The telescopic rod (21) passes through the sleeve rod (20) and is axially slidably connected to it.

3. A carbon dioxide storage tank for supercritical extraction according to claim 1, characterized in that: The inner wall of the inner cylinder (4) is provided with reinforcing ribs, which are annular ribs, longitudinal ribs or a combination thereof, and are distributed gradually from bottom to top along the axial direction of the inner cylinder (4).

4. A carbon dioxide storage tank for supercritical extraction according to claim 3, characterized in that: It also includes auxiliary mechanisms, which include: Balance tank (11), the balance tank (11) penetrates the upper cavity (7) of the inner cylinder (4), and the balance tank (11) is isolated from the upper cavity (7); The second piston (12) is disposed inside the balance tank (11), which is divided into a second balance chamber (13) and a connecting chamber (14). The second balance chamber (13) is a sealed chamber containing high-pressure gas. A balance hole is provided on the balance tank (11) to connect the connecting cavity (14) with the gas phase space of the outer cavity (5).

5. A carbon dioxide storage tank for supercritical extraction according to claim 4, characterized in that: Multiple balance tanks (11) are provided, and the multiple balance tanks (11) are evenly arranged around the inner cylinder (4).

6. A carbon dioxide storage tank for supercritical extraction according to claim 4, characterized in that: A connecting ring (15) is fixedly provided on the inner wall of the tank (1), and a sealing plate (16) is fixed on the inner wall of the connecting ring (15). The sealing plate (16) and the balance hole are arranged opposite each other in the axial direction so that when the inner cylinder (4) moves in the axial direction, the overlapping area of ​​the balance hole and the sealing plate (16) changes accordingly.

7. A carbon dioxide storage tank for supercritical extraction according to claim 5, characterized in that: The elastic support (10) includes a connecting piece (17) and a guide rod (18), the guide rod (18) passing through the connecting piece (17) and sliding vertically connected to it, for limiting the circumferential rotation and radial displacement of the inner cylinder (4).

8. A carbon dioxide storage tank for supercritical extraction according to claim 5, characterized in that: The elastic support (10) also includes a sleeve (19) and a shape memory alloy spring, which is sleeved on the guide rod (18) and its stiffness increases with increasing temperature and decreases with decreasing temperature.

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